1. Field of the Invention
The invention relates generally to inspection, repair, and replacement of pipeline risers, particularly components such as the flexible joints utilized therewith.
2. Background Art
Risers typically are used to connect a subsea wellhead assembly to a floating vessel. Typically, the lower end of a riser is connected to a wellhead assembly adjacent the ocean floor, and the upper end is operatively connected to the floating vessel such that a sealed connection is formed between the wellhead assembly and the floating vessel.
As production operations have progressed into deeper waters, the length of the riser also has increased. Due to the greater stresses placed upon such systems, riser structural failure may result if various stresses in the elements of the riser exceed the strength and fatigue limitations of the riser material. Flexible joints are typically used to mitigate stresses at the hang-off point while supporting the riser axial load.
As shown in FIG. 1, flexible joints 10 are typically installed as a component of the riser 11, or at the interface between the riser 11 and a floating structure or platform 13 to which the riser 11 is connected. Flexible joints 10 may comprise various configurations, including a ball joint to permit articulation of the riser 11 with respect to the floating structure 13 and may also include one or more elastomeric elements to facilitate relative motion between risers or between a riser and the operatively connected floating structure 13. Facilitation of relative movement by the elastomeric elements and other components of a flexible joint 10 effectively lessens the occurrence of damage due to the various forces and tensions occurring in the riser 11 and in the interface between riser 11 and platform 13.
FIG. 2 demonstrates one variation of an operative connection between a riser 11 and offshore platform 13. In this configuration, the flexible joint 10 is configured to operatively connect to a receptacle 14 of the offshore platform 13. At its other end, the flexible joint 10 is operatively connected to static spool piping 15 leading to the upper areas of the platform 13.
Flexible joints 10 and other components used in conjunction with offshore riser systems are often subjected to tremendous elastomeric strains and metal stresses. Over time, such strains, environmental factors, and other variables may result in damage to the flexible joints 10. Traditionally, the inspection or repair of a flexible joint 10 will involve a long period of decreased productivity during which production operations must be severely curtailed or discontinued while the riser 11 and flexible joint 10 are accessed, the flexible joint 10 is retrieved, removed from the riser 11 and a temporary workaround installed. After a separate off-site inspection and refurbishment or replacement of the flexible joint 10 is completed, the process is reversed to remove the workaround and install the replacement or refurbished flexible joint 10. The entire process will often result in a shutdown of production for many weeks, exposure of divers and other workers to dangerous conditions, and millions of dollars in lost production and productivity. Accordingly, there is a need for an improved method for inspecting, repairing, and/or replacing such flexible joints 11.